1. Field of the Invention
The present invention relates to image processing, more particularly, a method for detecting a boundary of a monetary banknote within an image.
2. Description of the Prior Art
Advancements in image processing systems, including digital color copiers, scanners, and small scale printing presses, has also lead to reproduction of monetary banknotes, currencies, stocks, bonds, and other irreproducible documents by counterfeiters. Obviously illegal, criminals participate in such activities for personal gain or profit.
Because of the presence of such counterfeit and copied items, there is a need to be able to effectively discern and distinguish such fake items from valid and authentic ones. This task however, becomes increasingly difficult as printing and reproduction advancements allow counterfeiters to reproduce copies that are virtually indistinguishable to the human eye.
One aspect of counterfeit currency detection involves identifying a boundary of a monetary banknote. FIG. 1 shows a monetary banknote 110 according to the prior art. Note that the banknote 110 can be separated into two main sections: the banknote boundary 120 and the banknote main body 130. It is therefore important to be able to identify the banknote boundary 120, because once identified, currency verification processes can take place within the banknote main body 130. The banknote main body 130 generally contains more distinguishable features, such as landmarks, holograms, colors, and texture patterns, where more secure counterfeit identification processes can occur. Also, distinguishing the banknote boundary 120 will allow different banknotes to be separated in the case they are overlapping, or if several banknotes are contained within the same scanned image.
Additionally, if the banknote is scanned while embedded in a complicated image background, it may be more difficult to distinguish the actual note from the image background. The image background may also provide additional noise and/or patterns to complicate the detection process and introduce irregularities and errors. Also, variations in the shift, rotation and alignment of the banknote may complicate identification processes. Therefore in these conditions, identification of the banknote boundary is crucial to avoid errors in counterfeit detection.